Qubit metrology of ultralow phase noise using randomized benchmarking
P. J. J. O'Malley, J. Kelly, R. Barends, B. Campbell, Y. Chen, Z., Chen, B. Chiaro, A. Dunsworth, A. G. Fowler, I.-C. Hoi, E. Jeffrey, A., Megrant, J. Mutus, C. Neill, C. Quintana, P. Roushan, D. Sank, A., Vainsencher, J. Wenner, T. C. White, A. N. Korotkov, A. N. Cleland
TL;DR
This paper introduces a randomized benchmarking-based metrological tool for ultralow phase noise measurement in qubits, revealing a telegraph noise mechanism in SQUID-based qubits beyond standard techniques.
Contribution
It develops a new method to measure dephasing with higher precision and uncovers a novel noise mechanism affecting qubit coherence.
Findings
The method enhances measurement precision of phase noise.
The SQUID qubit is not limited by 1/f flux noise at short times.
A telegraph noise mechanism was observed in the qubit.
Abstract
A precise measurement of dephasing over a range of timescales is critical for improving quantum gates beyond the error correction threshold. We present a metrological tool, based on randomized benchmarking, capable of greatly increasing the precision of Ramsey and spin echo sequences by the repeated but incoherent addition of phase noise. We find our SQUID-based qubit is not limited by flux noise at short timescales, but instead observe a telegraph noise mechanism that is not amenable to study with standard measurement techniques.
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